Protected dry-cell bobbin and method of making the same



pf i5 1924 c. w. amm-fa PROTECTED DRY GELL- BOBBIN AND THOD'O MAKING THE SAME Filed Feb.

n W M W n um .um uw patented Apr.. l5, E92@ testata earner este CLARENCE VJ. BRXZTE, GF FREMONT, OHIO, ASSGNOR TO yNATlONL CARBON GU.

DTC., A CORPORATON OF NEW' YORK.

ZPRQTECTEB DRY-CELL BOBBIN AND METHOD 0F MAKING TEE SAME.

Application tiled February 26, 392i. Serial No. M3241.

To ,all 'whom z5 may concern Y,

Be it known that L CLananonW. Beonait'n, a citizen of the United States, residing at Fremont, in the county of Sandusky and State of Ohio, have invented certain new and useful Improvements in Protected Dry- Cell loboins and -Methods oi Making the Senio, et which the following,- is a specitication. Y

This invention relates to improvements in that type of dry cells in which the cathode is a carbon rod carrying a molded mixbobliin or core. In cells or' this kind the loobliin is usually enclosed in a wrapper of ganze, cheese cloth or like fabric, suitably tied. in position.' '.he object of my invention is to eliminate the tediousand expensive operations of Wrapping and tying, by the substitution for the fabric of a more etiicient and economical protective means Molded nxix loolibinsnr'e relatively lfra ile. They are liliely to be injured hyhand ingA before insertion in the cells, and when inserted they may scale, or crumble due to the, softeninvl action of the electrolyte or for other reasons. As no isolating lining` for the active surface of the zine electrode .is usually provided in cells having?r the nxix in molded form, the crumbling?r of the liohhin is a serious disadvantage and niust be prevented. Particles of carhoimceous material ,and manganese dioxid may he dislodged when the bobbin is inserted or may work their Way or migrate through the paste. of excitant and come into contact with the zinc, ting up wasteful local action with perforation ol the zincand leakageot electrolyte. To prevent these and other troubles thc Wrav ping method referred to is now eommon y used.

have discovered that by procceding'as hereinafter fully set forth l obtain a protective bobbin coatingT which performs all the -useful functions of the gauze Wrapping? and is economical and easily applied, Broadly, 'the method consists in precipitating a chemical compound at. or near the cxterior surface of the hobloin.4

In the accompanying drawing illustrative of the invention, the .figure is a vertical central section through va dry cell. In this drawing, reference 'numeral l denotes a depolarizing core or hobbin formed about a carbon rod 2 and inserted in a metal electrode 3 containing excitant 4. The protective coating 5, hereinafter'described in detail, overlies thaloohhin surface and pen lmentes the outer portion of the. mix7 secureig.' bonding the saine. The bolihin may rest ou aspaeing disc d A, seal 7 closes the cell.

ln the preferred embodiment oi my intenw tion, hobbins containing a salt ot' an allmline earth metal, e. g. calcium or hariuin chlorid, are brought into Contact with a solution of a soluble sulfate, ior c:\'ainple, aininoniuni sulfate or zinc sulfate. By the resulti1igtl iiilile decomposition an insoluble superiicial layer'of calcium or barium sul fate is formed upon the hohbin. This layer of precipitated salt acts as a cement or hinder, unitying and strengthening the es posed suri'acc of.t .he mix. .Bobbins so protected may be safely handled and (lo/not disinte rate in use.

.A kaline 'earth metal chlorid in quantity' in excess of that required to produce the coating is preferably incorporated with the mix ingredients before molding'. l Forexample, a mixcomprising manganese dioxid and carbon or graphite may be inoistened with the usual electrolyte of zinc chlorid and ammonium ehlorid, to which has been added the proper amount of alkaline earth metal chlorid. The quantity of the ehlorid may he varied within Widelimits louty l prefer to use it in the proportion of approximately 6 parts by weight. of dry chlorid to `l00 parts ot mix. The nioistened materials are then inoldcd about a carbon rod, and the bobbin so formed is in'iinersed in a solution o't' a sulfate7 forming the cementing precipitate. The cell may hy inserting the protected liohbin axially in a Zinc container', applying excitant aste between lthe hobliin and container, in the customary manner.

The thicknessof the protective layer may oi course be regulated by varying the conu centration of the reacting solutions and the time of immersion in the preeipitant. In general. a superficial coating only is ref quired. By examining a treated boohin the depth to which precipitationhas extended may be readily determined and the concentration and time of reaction adjusted to ob- -tain a greater or less 4depth as desired. The

character of the coating will depend sornewhat upon the nature of the mix materials. l have found that a firmer, smoother coating may be obtained if the carbonaoeous mateand sealingy CJI i rial and depolarizer are very finely divided,

and I prefer to pass these materials through at least a hundred-mesh screen.

Instead of incorporating the alkaline earth metal chlorid with the electrolyte be- 'tore molding, the bobbin in molded form line earth metal chlorid, being adjacent to the surface impregnated by the sulfate, will' `react. with it. The presence of alkaline earth 'tageous, tending to prevent metal chlorids in the dry'cell mix is advair gassing, as has been shown inv the patent application ot' Anna F. MacKenzie7 Ser. No. November Ll, 1920. For this reason I prefer to disseminate the chlorid throughout the entire mass of the bobbin using an excess as described above.

While the metathesis ot two salts is probably the most convenient way of obtaining the cementing precipitate7 it is evident that other types ot' reaction may be employed. For example, an alkaline earth metal oxid or hydroxid may be caused to react. at the -surface of the bobbin with a soluble sulfate or sulfuric acid. In any case thel treated bobbin 'maydie washed or neutralized, though this will not in general be necessary.

The invention is not limited "to the formation ot insoluble sultates'upou the bobbin surface, as many other precipitations in situ will have a satisfactory' binding action. For example, I have used phosphates in this connection with advantage. A I

From the foregoing description it will be 'clear that thefmaking of a protected bobbin according to invention involves only processeswhich can be carried out mechanically 'and simultaneously upon a large number of elements. sIt has been found in practice" that bobbins Ithus precipitation are self-sustaining and free from tendency to` crumble Also, the, in-

nani, filed Y indurated by soluble coating does not appreciablyincrease the internal resistance of the cell nor diminish the porosity otthc mix, and the coating volume is relatively so small that the capacity ot the cell for holding active mate- `rial is practically undiminished.

lin water or the electrolyte ot dry cells.

I claim:

l. Ina process ol making a protected bobbin. applyiug'to the bobbin a solution containing a precipitable material, and then reacting upon the solution with a precipitaiit for such material.

In a process ot makinga protectedk bobbiii chemically, precipitating an insolu-f ble sulfate upon and beneath the surface of the bobbin.

3.111 a process ot making a protected bobbin, precipitating barium sulfate lupon and beneath the surface of, the bobbin.

4. In a process ot' making a protected bobbin, adding to the usual bobbin constitu-l ents an additional substance, and applying a material adapted to form a precipitate with said substance.

5. In a process o't making a protected bobbin, incorporating with the usual bobbin constituents an additional substance, molding a bobbin containing said constituents and substance, and applying to the molded bobbin a material adapted to form a precipitate with said substance.

6. In a process of making a protected bobbin, incorporating an alkaline earth metal clilorid withthe usual bobbin constituents, molding a bobbin therefrom` and applying a soluble sulfate to the molded bobbin.

7. A dry cell bobbin provided with a coat-v ing of'barium sulfate. v

In testimony whereof I atliX my signature.

CLARENCE W. BROKATE. 

